Den nyeste forskning viser....

Kjeld Jul skrev:
Den Antarktiske halvø ligger i et område med vulkansk aktivitet,denne termiske påvirkning er højst sandsynlig årsagen til den større opvarmning på vest Antarktis.

A new NASA study adds evidence that a geothermal heat source called a mantle plume lies deep below Antarctica's Marie Byrd Land, explaining some of the melting that creates lakes and rivers under the ice sheet. Although the heat source isn't a new or increasing threat to the West Antarctic ice sheet, it may help explain why the ice sheet collapsed rapidly in an earlier era of rapid climate change, and why it is so unstable today.

4. Conclusions

The current tropospheric temperature trend from 1979-2016 is influenced by large, natural, interannual fluctuations which if removed reveal a trend about a third less positive than is directly measured (+0.155 down to +0.095 K dec−1). This underlying trend is essentially the same as calculated in CM94 (+0.09 K dec−1) when only 15 years were available and who determined the underlying trend at that time needed adjustment upward, from −0.04 to +0.09 K dec−1.
...
If we assume, among other things, that the impact of the net of natural external and internal forcing variations has not influenced the observed trend and that anthropogenic forcing as depicted in the average of the IPCC AR5 models is similar to that experienced by the Earth, then observations suggest the tropospheric transient climate response (TTCR) is 1.10 ± 0.26 K. This central estimate is likely less than half that of the average of the 102 simulations of the CMIP-5 RCP4.5 model runs also examined here (2.31 ± 0.20).
...

Abstract

Sea-level rise and climatic change threaten the existence of atoll nations. Inundation and erosion are expected to render islands uninhabitable over the next century, forcing human migration. Here we present analysis of shoreline change in all 101 islands in the Pacific atoll nation of Tuvalu. Using remotely sensed data, change is analysed over the past four decades, a period when local sea level has risen at twice the global average (~3.90 ± 0.4 mm.yr−1). Results highlight a net increase in land area in Tuvalu of 73.5 ha (2.9%), despite sea-level rise, and land area increase in eight of nine atolls. Island change has lacked uniformity with 74% increasing and 27% decreasing in size. Results challenge perceptions of island loss, showing islands are dynamic features that will persist as sites for habitation over the next century, presenting alternate opportunities for adaptation that embrace the heterogeneity of island types and their dynamics.

John Niclasen skrev:
Finder der nogle alarmistiske påstande overhovedet, som holder stik ved nærmere eftersyn!?

Over the last decade, the solar wind has exhibited low densities and magnetic field strengths, representing anomalous states that have never been observed during the space age. As discussed by Schwadron et al. (2014a), the cycle 23–24 solar activity led to the longest solar minimum in more than 80 years and continued into the "mini" solar maximum of cycle 24. During this weak activity, we observed galactic cosmic ray fluxes that exceeded the levels observed throughout the space age, and we observed small solar energetic particle events.

This led to a projection of dose rates from galactic cosmic rays on the lunar surface, which suggested a ∼20% increase of dose rates from one solar minimum to the next, and indicated that the radiation environment in space may be a worsening factor important for consideration in future planning of human space exploration. We compare the predictions of Schwadron et al. (2014a) with the actual dose rates observed by CRaTER in the last 4 years. The observed dose rates exceed the predictions by ∼10%, showing that the radiation environment is worsening more rapidly than previously estimated.

The causes that are controlling the decrease in sea ice are still under discussion. In several studies changes in extent, thickness and drift of Arctic sea ice are related to changes in the overall atmospheric circulation patterns as reflected in the North Atlantic Oscillation (NAO) and Arctic Oscillation (AO). The NAO and AO are influencing changes of the relative position and strength of the two major surface-current systems of the Arctic Ocean.

The increase in sea ice extent during the late Holocene seems to be a circum-Arctic phenomenon, coinciding with major glacier advances on Franz Josef Land, Spitsbergen and Scandinavia. The increase in sea ice may have resulted from the continuing cooling trend due to decreased solar insolation and reduced heat flow from the Pacific.

The increase in sea ice extent during the late Holocene seems to be a circum-Arctic phenomenon as PIP25-based sea ice records from the Fram Strait, Laptev Sea, East Siberian Sea and Chukchi Sea display a generally quite similar evolution, all coinciding with the decrease in solar radiation.

The main factors controlling the millennial variability in sea ice and surface-water productivity are probably changes in surface water and heat flow from the Pacific into the Arctic Ocean as well as the long-term decrease in summer insolation, whereas short-term centennial variability observed in the high-resolution middle Holocene record was possibly triggered by solar forcing.

crank skrev:
John >

Hvorfor finder du anledning til at poste den textblok lige her lige nu?

Jeg kørte den lige igennem Google Translate, så man kan se, at det er noget med forhistorisk tid:

Årsagerne til at kontrollere nedgangen i havsisen er stadig under drøftelse. I flere studier er ændringer i omfang, tykkelse og drift af arktisk hav is relateret til ændringer i de samlede atmosfæriske cirkulationsmønstre som afspejlet i Nordatlantisk Oscillation (NAO) og Arctic Oscillation (AO). NAO og AO påvirker ændringer i den relative position og styrken af ​​de to store overfladestrømssystemer i Det arktiske hav.

Forøgelsen af ​​havets udstrækning i løbet af det sene Holocene synes at være et omarktisk fænomen, der falder sammen med store gletsjereforstærkninger på Franz Josef Land, Spitsbergen og Skandinavien. Stigningen i havis kan skyldes den fortsatte køletrend på grund af faldende solisolering og reduceret varmestrøm fra Stillehavet.

Forøgelsen af ​​havets udstrækning i løbet af det sene Holocene synes at være et omarktisk fænomen, da PIP25-baserede havskibe fra Fremstrædet, Laptevhavet, Østsibiriskehavet og Chukchihavet viser en generelt ret tilsvarende udvikling, som alle sammenfaldende med fald i solstråling.

De vigtigste faktorer, der styrer den årtusinde variabilitet i havis og overfladevandsproduktivitet, er sandsynligvis ændringer i overfladevand og varmestrøm fra Stillehavet til Det arktiske hav såvel som det langsigtede fald i sommersolskab, hvorimod kortsigtet århundredesvariation observeret i high-resolution midten holocene record blev muligvis udløst af solstråling.



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Morten Riber skrev:

Crank kan altid finde på noget at strinte med når John har lagt et indlæg ind. Der er igen et fint eksempel på hvordan Crank sander forummet til.

crank skrev:

Morten Riber skrev:

Crank kan altid finde på noget at strinte med når John har lagt et indlæg ind. Der er igen et fint eksempel på hvordan Crank sander forummet til.

Nå. Nu har jeg jo aldrig påstået, at jeg var perfekt!

Men, har du nogensinde bidraget med nogetsomhelst andet end smagsdommeri, Morten?



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We consider the Koch ice index which describes the amount of ice sighted from Iceland, in the period 1150 to 1983 AD. This measure of ice extent is a non-linear and curtailed measure of the amount of ice in the Greenland Sea, but gives an overall view of the amounts of ice there through more than 800 years. The length of the series allows insight into the natural variability of ice extent and this understanding can be used to evaluate modern-day variations. Thus we find that the recently reported retreat of the ice in the Greenland Sea may be related to the termination of the so-called Little Ice Age in the early twentieth century. We also look at the approximately 80 year variability of the Koch (sea ice) index and compare it to the similar periodicity found in the solar cycle length, which is a measure of solar activity. A close correlation (R=0.67) of high significance (0.5 % probability of a chance occurrence) is found between the two patterns, suggesting a link from solar activity to the Arctic Ocean climate.

The 'low frequency oscillation' that dominated the ice export through the Fram Strait as well as the extension of the sea-ice in the Greenland Sea and Davis Strait in the twentieth century may therefore be regarded as part of a pattern that has existed through at least four centuries. The pattern is a natural feature, related to varying solar activity. The considerations of the impact of natural sources of variability on arctic ice extent are of relevance for concerns that the current withdrawal of ice may entirely be due to human activity. Apparently, a considerable fraction of the current withdrawal could be a natural occurrence.

John Niclasen skrev:
Stein et al. (2017):

Holocene variability in sea ice cover, primary production, and Pacific-Water inflow and climate change in the Chukchi and East Siberian Seas (Arctic Ocean)

The causes that are controlling the decrease in sea ice are still under discussion. In several studies changes in extent, thickness and drift of Arctic sea ice are related to changes in the overall atmospheric circulation patterns as reflected in the North Atlantic Oscillation (NAO) and Arctic Oscillation (AO). The NAO and AO are influencing changes of the relative position and strength of the two major surface-current systems of the Arctic Ocean.

The increase in sea ice extent during the late Holocene seems to be a circum-Arctic phenomenon, coinciding with major glacier advances on Franz Josef Land, Spitsbergen and Scandinavia. The increase in sea ice may have resulted from the continuing cooling trend due to decreased solar insolation and reduced heat flow from the Pacific.

The increase in sea ice extent during the late Holocene seems to be a circum-Arctic phenomenon as PIP25-based sea ice records from the Fram Strait, Laptev Sea, East Siberian Sea and Chukchi Sea display a generally quite similar evolution, all coinciding with the decrease in solar radiation.

The main factors controlling the millennial variability in sea ice and surface-water productivity are probably changes in surface water and heat flow from the Pacific into the Arctic Ocean as well as the long-term decrease in summer insolation, whereas short-term centennial variability observed in the high-resolution middle Holocene record was possibly triggered by solar forcing.

Via: New Paper Indicates There Is More Arctic Sea Ice Now Than For Nearly All Of The Last 10,000 Years @ NoTricksZone

christian-roskilde skrev:
hvor meget af de senere års is afsmeltning bliver medtaget i grafikken så vi kan sætte nuværende minimum i perspektiv?